Beta testers have received access to a release candidate of Windows XP Service Pack 3, but general consumers still have a long wait until they'll see SP3 available for download. Microsoft has scheduled the last major update to its six-year-old OS for the first half of 2008 - likely after Windows Vista SP1.
Around 15,000 testers now have access to XP SP3, and Microsoft says it plans one last public beta release before releasing the final bits next year. The same individuals are testing Vista SP1 RC Preview, although Microsoft has also promised a public SP1 build. Although XP SP3 is more of a roll-up of existing hotfixes and should be completed before Vista's first upgrade, Microsoft will likely delay its release and use SP1 to encourage holdout XP users to upgrade to Vista.
News source: BetaNews